We are studying the structural relationships of proteins found in RNA tumor viruses, particularly Rous sarcoma virus and Rous-associated virus 61. This includes studies on the topography of proteins in the virion using reversible chemical crosslinkers on two dimensional polyacrylamide gels and translation of viral RNAs in cell-free extracts of reticulocytes. Some objectives include clarifying the translation order of p12 and p27 in the gag-complex, and studying the factors controlling synthesis and processing of the gag, gag-pol and env proteins.